Non-invasive assessment of left ventricular function using rate variability of a left ventricular assist device

The left ventricular assist device (LVAD) developed by Arrow International (Reading, PA) is intended for destination therapy for end-stage heart disease. The LVAD inlet cannula is positioned in the left ventricular apex, and the outlet is anastomosed to the ascending aorta. The LVAD rate is controlled automatically in response to filling pressure. Assessment of left ventricular function is desirable as a diagnostic tool for patient care, and potentially as an indicator of myocardial recovery. This study investigates the effect of native heart contractility on LVAD dynamics using a mock circulatory loop. The native heart is simulated by a pulsatile pneumatic pump. Native heart contractility is controlled by the pneumatic pump systolic pressure. LVAD rate is measured using the system power waveform. Other LVAD parameters are measured via wireless telemetry from the LVAD controller. With a non-functioning left ventricle, the LVAD rate varies about the mean at a frequency of approximately 0.05 Hz. As contractility increases, the LVAD rate variability increases in frequency and amplitude. The ratio of spectral energy at frequencies above and below 0.1 Hz was found to correlate with pneumatic pump contractility (systolic pressure), changing by an order of magnitude over a range of systolic pressure of 0-150 mmHg. The variability of other LVAD parameters was also investigated.